Hi [image: :)] 

 

I'm new to Rails. I'm trying to make an app where students can login in and 
signup for the exam. I have a problem filtering data, where a student can 
only see exams which belong to her/his year and department. 

 

Subject has the following columns:
    t.string  "name"
    t.integer "ects"
    t.integer "year"
    t.integer "professor_id" (foreign key which relates it to professor). 
 
Its relationship with exam: 
has_one :exam 
 
Exam has the following columns:
    t.date    "start_date"
    t.string  "department"
    t.integer "professor_id"
    t.integer "subject_id"  
 
Its relationship with exam: 
 belongs_to :subject 
 
User has attributes year (year of study) and department. The problem is 
that exam only has depatment, but it doesn't have year. 
 
I have made this in exam.rb 
 
scope :department, -> (department) { where('department == ?', department) }
scope :year, -> (year) { where('subject.year == ?', year) } 
 
Then I called these methods in exams controller (index action) and passed 
the data:
 
 @exams = Exam.department(current_user.department) && 
Exam.year(current_user.year)
 
There is a problem with a scope year, it doesn't recognize subject. When I 
try to access the list of exams it says this: 
SQLite3::SQLException: no such column: subject.year: SELECT "exams".* FROM 
"exams" WHERE (subject.year == 2)
 
But when I include subject_id:  scope :year, -> (year) { 
where('Subject.find(:subject_id).year == ?', year) }
It says there is a syntax error: SQLite3::SQLException: near "(": syntax 
error: SELECT "exams".* FROM "exams" WHERE (Subject.find(:subject_id).year 
== 2). 
 
I have tried accessing subject attributes by using delegate and to_params, 
but it didn't help. I've been googling this issue for more than 10 days, 
but I haven't been able to find a solution. 
 
I appreciate any kind of help. Thanks in advance [image: :)] 
 
 

 

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